Our school purchased three Sony VPL EX4 projectors in September 2007. In February 2008 all three bulbs blew and the projectors were returned to Sony who told us that they had not been correctly maintained. Since that time we have employed a technician who has been responsible for cleaning the projectors following Sonys recommendations. Dates of cleaning were logged. In December 2008 two bulbs once again blew and all three projectors were sent back to Sony, once again we were told that the projectors were full of dust and the faults were caused by improper or insufficient cleaning of the product. We also have six Sanyo digital projectors in school, which are between 4 and 6 years old and have been totally reliable. We are now in a position that we need to spend another £220 on a bulb for one Sony projector, another projector has poor imaging and the third I have been advised is not worth the repair costs. I now have no confidence in a brand I have always used and trusted. These projectors have an inefficient filter and fan system which causes dust to penetrate the units. I would not recommend anyone to buy them for classroom use.